Such valve devices are known from the prior art. A commonly marketed pressure shut-off valve has a pressure limiting valve controlled externally by the consumer pressure and a non-return valve. The pressure shut-off valve is mainly used in dual-circuit hydraulic systems, which have a low-pressure circuit with a low-pressure pump and a high-pressure circuit with a high-pressure pump. The volume flow rates of the hydraulic circuits are combined for the same consumer. The low-pressure circuit usually undertakes the rapid movement of the consumer at a lower pressure and a higher volume flow rate. The high-pressure circuit ensures the subsequent application of force, in the case of tensioning, for example, at a higher pressure and a lower volume flow rate. The high-pressure circuit is additionally usually protected by its own pressure limiting valve.
The pressure shut-off valve is used for the pressure-dependent shut-off of the delivery flow of the low-pressure circuit. As soon as the shut-off pressure set at the pressure limiting valve is reached at the consumer, the pressure limiting valve is fully opened. In this way, the fluid pressure upstream of the non-return valve drops, so that the non-return valve closes and separates the consumer from the low-pressure pump. The delivery flow of the low-pressure pump is thus switched to low-loss circulation to the tank via the fully opened pressure limiting valve. In this state, only the high-pressure pump is still supplying the consumer. If the consumer pressure again sinks below a set shut-off pressure, the low-pressure delivery flow is again connected to the consumer.
A constant demand on the part of the users of such pressure shut-off valves is for the valves to be produced in a more compact form and more economically, designed to function reliably.
In addition to the above-mentioned general pressure shut-off valves, specialized valve devices are also used in hydraulics, which are intended for the controlled loading and, if necessary, reloading of storage-capable hydraulic systems, in particular hydraulic accumulators or accumulators. In such arrangements, usually only a pressure circuit or a pump is used. When a desired, predefinable pressure is reached in the accumulator, a pressure limiting valve switches the pump volume flow rate to low-loss circulation, while a non-return valve ensures that the pressure in the storage-capable hydraulic system is maintained. Characteristic of such valve arrangements, which are also referred to as accumulator charging valves, is the behavior in the case of dropping pressure in the storage-capable hydraulic system. If the accumulator pressure drops as a result of a temperature change, a leakage, or as a result of conventional consumption, the valve device ensures that the pressure limiting valve does not close again immediately, thus initiating the reloading process. Instead the closing of the pressure limiting valve occurs only when a predefinable limit pressure is not reached. Due to this measure, the storage-capable hydraulic system is reloaded less often. The known accumulator charging valves require a very large installation space, however.